Multimode power amplifier and method of switching among multiple modes thereof, and mobile terminal

ABSTRACT

Disclosed are a multimode power amplifier, also a method for implementing different work mode switching by the multimode power amplifier and a mobile terminal using the multimode power amplifier. The multimode power amplifier includes at least two stage amplification circuits, each stage amplification circuit is connected in serial way; each stage amplification circuit has at least one basic amplification unit array, the amplification unit array is composed of multiple basic amplification units in parallel way. Bias voltage of each basic amplification unit array is controlled independently. By configuring the bias voltage flexibly, the multimode power amplifier can implement the switching between saturation mode and linear mode, and meets the actual needs of multi-communication mode. In addition, the multimode power amplifier also has the advantages of lower cost, simple and flexible circuit, and easy realization.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is the U.S. National Stage of International Application No.PCT/CN2013/078707, filed Jul. 2, 2013, which was published in Chineseunder PCT Article 21(2), which in turn claims the benefit of ChinaPatent Application No. 201210298572.3, filed Aug. 21, 2012.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power amplifier (PA), and morespecifically, to a multimode PA that accommodates both saturated andlinear modes, and thus is capable of adapting to a plurality oftelecommunication formats. The present invention also relates to amethod of switching among different operating modes with the multimodePA and a mobile terminal that uses the multimode PA. The presentinvention, therefore, is in the field of PA technology.

2. Description of the Prior Art

With the third generation (3G) mobile telecommunication technologydeployed on a largescale, 2G and 3G standards will coexist for a longperiod of time. Therefore, the resources telecommunication operatorsinvested on 2G deployment would not be wasted while the operators arephasing-in 3G smoothly so to lower the cost. Currently, three 3Gstandards—TD-SCDMA, CDMA2000 and WCDMA 3-co-exist in the Chinese market.In addition, Wi-Fi and WiMax, as supplementary technology of 3G-LTE,also have significant potential. Thus, the market environment in which aplurality of telecommunication standards co-exists requires moreadaptability from mobile terminals.

Multimode technologies comprise the multimode adaptability of basestations and mobile terminals. With mobile terminals, the multimodeadaptability cannot be realized without a multimode power amplifier(PA). In general, there are two types of PAs: PAs operating insaturation mode or in linear mode. A saturated PA is needed in theGlobal System for Mobile Communication (GSM) system. It adopts GMSKmodulation and is capable of compressing the amplitude of its radiofrequency (RF) signals as the signals do not contain modulationinformation. In a CDMA-based 3G system, such as EDGE, TD-SCDMA, TD-LTEor CDMA2000, a linear PA is required.

One feature of a PA in saturation mode is that within a certain range ofinput power, the output power is not determined by the input power butby the power supply of the PA's output stage and the load impedance.With a PA in linear mode, the output power is always proportional to theinput power. Even with telecommunication standards that require a linearPA, such as EDGE, TD-SCDMA, TD-LTE, or WCDMA, the requirements on thePA's output power, gain and current may differ as the internet standardmay be different. This analysis shows that a saturation PA and a linearPA requires completely different design, and the transistor parametersand operating current that meet the requirement of their respectivecircuits are very different.

In order to meet the requirements imposed by different telecommunicationstandards to a PA, the current technology usually apply several singlemode PAs coupled with a gating switch. However, the method significantlyincreases the cost. For example, a Chinese patent application number201110346135.X, disclosed a power amplifying module, a multimode RFtransceiver, a RF front-end module, a multimode terminal module and amethod of sending signals from a multimode terminal. The patentcomprises two operating modes, the first is GSM-mode signals and thesecond is TD-SCDMA-mode signals. When the controlling signal is alow-frequency signal in the first mode, the controller sends a signal ofsaturation mode to the low-frequency amplifier. When the controllingsignal is a high-frequency signal in the first mode, the controllersends a signal of saturation mode to the high-frequency amplifier. Whenthe controlling signal is in the second mode, the controller sends asignal of linear mode to the high-frequency amplifier.

A Korean patent application number KR 10-2010-0051808, discloses adevice and method that assembles power amplifying units in one module tosupport multimode mobile terminals, so to reduce the space and cost ofmultimode mobile terminals. The PA of mobile terminals comprises a firstamplifying unit and a second amplifying unit. The first amplifying unitdefines the four bands of GSM as low-frequency bands and high-frequencybands, and then amplifies signals of the low-frequency bands. The secondamplifying unit amplifies signals of the high-frequency bands andTD-SCDMA signals, with both signals selected by a TD-SCDMA controllingand switching unit.

In addition, a U.S. patent application Ser. No. 09/455,813, introduces aPA comprising a carrier amplifier and a peak amplifier for multimodemobile telecommunication devices. The peak amplifier has an adjustablebias voltage, so that a regulator can adjust the voltage to apredetermined level according to the selected telecommunication mode.The bias voltage of the peak amplifier maintains the same as long as thecommunication mode stays the same. The modulation efficiency andlinearity of a specific telecommunication mode can be optimized byadjusting bias points of the peak amplifier that are relevant to theselected telecommunication mode.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide a multimodepower amplifier (PA) which accommodates both saturated and linear modes,so to adapt to an environment in which multiple telecommunication modesco-exist.

Another object of the present invention is to provide a method by whichthe multimode power amplifier switches among different operating modes.

A third object of the present invention is to provide a mobile terminalthat uses the multimode power amplifier.

In order to achieve these objects, the present invention provides thefollowing technical solutions: a multimode PA, a method of switchingamong different modes, and a mobile terminal.

The multimode PA of the present invention comprises two or more stagesof amplifier circuits connected in cascade.

Amplifier circuits at each stage have one or more basic amplifying unitarray. The amplifying unit array comprises a plurality of basicamplifying units connected in parallel.

Each basic amplifying unit comprises a capacitor, an amplifyingtransistor and a resistor. The capacitor connects, at one end, a radiofrequency (RF) signal input terminal, and at another end, a base of theamplifying transistor. The resistor connects, at one end, a bias voltageterminal, and at another end, the base of the amplifying transistor. Thecollector of the amplifying transistor is connected to the supplyvoltage terminal.

Preferably, a supply voltage terminal of an amplifier circuit in theprevious stage couples RF signals to the RF signal input terminal of anamplifier circuit in the next stage.

Preferably, an inductor is installed between the voltage source terminalof the amplifier circuit in the previous stage and the RF signal inputterminal of the amplifier circuit in the next stage.

Preferably, the emitter of the amplifying transistor of each basicamplifying unit is connected to a reference voltage.

Preferably, the bias voltage of each basic amplifying unit array iscontrolled independently.

The present invention also provides a method of switching amongdifferent modes to put the multimode PA into practice. The methodcomprises the following steps:

Exercise independent control over the bias voltage of each basicamplifying unit array of each amplifier circuit of the multimode PA.

Adjust the bias voltage of each basic amplifying unit array, so that allamplifying transistors are turned on when the multimode PA maintains asaturation mode.

Adjust the bias voltage of each basic amplifying unit array so that someamplifying transistors are turned on when the multimode PA maintains alinear mode.

Preferably, turn on the predetermined basic amplifying units throughconfiguring the bias voltage in different linear modes, and optimizeperformances in different linear modes through adjusting the biasvoltage.

Preferably, if the multimode PA must cover different telecommunicationstandards or different power modes in a specific telecommunicationstandard, it can be achieved by adjusting the number of basic amplifyingunits that are on or off, and the bias voltage of the basic amplifyingunits that are turned on. Or, it can also be achieved by dividing thepredetermined basic amplifying unit arrays into smaller basic amplifyingunit arrays, and adjusting the bias voltage of each smaller basicamplifying unit arrays individually.

The present invention further provides a mobile terminal equipped withthe multimode PA of the present invention.

The multimode PA of the present invention can configure flexibly thebias voltage and realize various combinations of saturated and linearmodes, so to meet the actual requirements of a plurality oftelecommunication standards, including EDGE, TD-SCDMA, TD-LTE and CDMA2000. In addition, the multimode PA costs less, has simple and flexiblecircuits, and is easy to realize.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing one basic amplifying unit of themultimode PA.

FIG. 2 is a diagram showing one basic amplifying unit array composed ofa plurality of basic amplifying units connected in parallel.

FIG. 3 is a simplified diagram of the basic amplifying unit array inFIG. 2.

FIG. 4 shows a circuit diagram of a multimode PA with a two-stageamplifier circuit.

FIG. 5 shows a circuit diagram of a multimode PA with a three-stageamplifier circuit.

FIG. 6 shows a circuit diagram of a multimode PA with a four-stageamplifier circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A detailed explanation of the present invention supplemented by figuresand implementation specifics are provided below.

A multimode power amplifier (PA), generally, comprises two basic typesof PAs: PAs in saturation mode or in linear mode. A PA operating inlinear mode usually needs to cover different telecommunicationstandards, such as EDGE, TD-SCDMA, SCDMA, TD-LTE, and so on. With agiven telecommunication standard (e.g. WCDMA), a linear PA often needsto have different power (or gain) modes, such as high-power (high-gain)mode, median-power (median-gain) mode, and low-power (low-gain) mode.

To meet the needs, the multimode PA of the present invention comprises X(a positive integer) basic amplifying units connected in parallel orcascade. The basic amplifying units can be turned on or off, orconfigured for different power modes through a bias voltage, thus agating switch is no longer needed. The basic amplifying units can bereused in different telecommunication mode. The optimum current andcircuit performance are achieved through adjusting and optimizing thebias voltage in different telecommunication modes. A more detaileddescription is provided below.

FIG. 1 is a circuit diagram showing one basic amplifying unit of themultimode PA. The basic amplifying unit, used to realize the basicamplifying function of the multimode PA, comprises a capacitor 105, anamplifying transistor 106 and a resistor 107. The capacitor 105, at oneend, connects to the RF signal input terminal so to receive an inputtedRF signal 101; and at another end, connects to the base of theamplifying transistor 106, so to couple the RF signal 101 to the base ofthe amplifying transistor 106 through the capacitor 105. The resistor107, at one end, connects to a bias voltage terminal so to receive abias voltage 102, and at another end, connects to the base of theamplifying transistor 106 so that the bias voltage 102 can providedirect current to the amplifying transistor 106 through the resistor107. A collector of the amplifying transistor 106 connects to a supplyvoltage terminal 103 so to couple the voltage source to the collector ofthe amplifying transistor 106 through an inductor. The emitter of theamplifying transistor 106 connects to the reference voltage 104. Theadjustment of the bias voltage can be made by a complementarymetal-oxide-semiconductor (CMOS) circuit. It is a regular design thatcan be delivered by any electronics technician, and requires no furtherexplanation.

FIG. 2 is a diagram showing one basic amplifying unit array composed ofX basic amplifying units connected in parallel. FIG. 2 shows only threebasic amplifying units and omits other units. A RF signal input terminal201 connects to RF signal input terminals (such as 205, 209 and 213 inFIG. 2) of X basic amplifying units respectively. A bias voltageterminal 202 connects to bias voltage terminals (such as 206, 210 and214 in FIG. 2) of X basic amplifying units respectively. A supplyvoltage terminal 203 connects to supply voltage terminals (such as 207,211 and 215 in FIG. 2) of X basic amplifying units respectively. Areference voltage terminal 204 connects to reference voltage terminals(such as 208, 212 and 216 in FIG. 2) of X basic amplifying unitsrespectively. FIG. 3 is a simplified diagram of the basic amplifyingunit array in FIG. 2, and used in FIG. 4. FIG. 3 shows an equation, M=X,meaning that the basic amplifying unit array is composed of X basicamplifying units connected in parallel.

FIG. 4 shows a circuit diagram of a multimode PA with a two-stageamplifier circuit. The RF signal input terminal 401 connects to anamplifier circuit 404 at the first stage, which is connected to anamplifier circuit 413 at the second stage in cascade. The amplifiercircuit 404 at the first stage is composed of a basic amplifying unitarray 405 connecting a basic amplifying unit array 407 in parallel. Thebasic amplifying unit array 405 is composed of A (a positive integer)basic amplifying units connected in parallel, and the basic amplifyingunit array 407 is composed of B (a positive integer) basic amplifyingunits connected in parallel. A bias voltage 406 provides direct currentbias to the basic amplifying unit array 405. A bias voltage 408 providesdirect current bias to the basic amplifying unit array 407.Correspondingly, a reference voltage 409 provides reference voltage tothe basic amplifying unit array 404, and a reference voltage 418provides reference voltage to the basic amplifying unit array 413. Asupply voltage terminal 402 of the amplifier circuit 404 at the firststage couples RF signals to a RF signal input terminal 410 of theamplifier circuit 413 at the second stage through an inductor 403. Theamplifier circuit 413 at the second stage comprises basic amplifyingunit arrays 414 and 416 connected in parallel. The amplifying unit array414 comprises C (a positive integer) basic amplifying units connected inparallel, and the basic amplifying unit array 416 comprises D (apositive integer) basic amplifying units connected in parallel. A biasvoltage 415 provides direct current bias to the basic amplifying unitarray 414, and a bias voltage 417 provides direct current bias to thebasic amplifying unit array 416. The amplifier circuit 413 at the secondstage connects to the supply voltage terminal 411 through an inductor412, and couples RF signals to an output matching network 420 at a node419, and completes outputting signals at a RF signal output terminal421.

FIG. 4 shows that an obvious feature of the multimode PA is thatpredetermined basic amplifying units can be turned on or off through aflexible configuration of bias voltages. In other words, the PA enablessome basic amplifying units operate (to amplify or in saturation mode)and cut-off, involving or not involving in the amplification. Forexample, a bipolar transistor is stopped if its emitter junction andcollector junction are reverse-biased through adjusting the biasvoltage. The transistor is amplifying if the emitter junction isforward-biased and the collector junction is reverse-biased throughadjusting the bias voltage. The transistor is saturated if the emitterjunction and collector junction are forward-biased through adjusting thebias voltage.

With field-effect transistors (FET), the relationship between theadjustment of bias voltage and operating modes is similar. Please referto relevant product manuals for specific parameters.

Therefore, the basic amplifying units can be used in both the saturatedand linear modes, and can realize a plurality of combinations ofdifferent saturated and linear modes in one multimode PA. When switchingamong different modes, the multimode PA does not need a gating switch orextra amplifier circuits. In addition, each amplifying unit can havedifferent operating currents in different modes so to further optimizethe amplifier's performance in different operating modes.

For example, when the multimode PA is in saturation mode, it has alarger regular power output. Thus the number of basic amplifying unitsoperating regularly is the largest, so is the operating current of thecircuit. If the multimode PA shown in FIG. 4 is operating in saturationmode, all basic amplifying unit arrays 405, 407, 414 and 416 would beturned on. Through adjusting and optimizing the numbers, A, B, C, D, ofbasic amplifying units of the basic amplifying unit arrays, and thelevel of the bias voltages 406, 408, 415 and 417, a designatedperformance requirement in the saturate mode can be achieved.

When the multimode power amplifier is in linear mode, the number ofbasic amplifying unit operating regularly is less than that insaturation mode, and the operating current is much lower than that insaturation mode. Therefore, some basic amplifying units can be turnedoff through controlling the bias voltages. For example, in FIG. 4, thebasic amplifying units in the basic amplifying unit arrays 405 and 414can be turned off through controlling the bias voltages 406 and 415; andthe basic amplifying units in the basic amplifying unit arrays 407 and416 can be turned on through controlling the bias voltages 408 and 417.Thus, corresponding technical requirements can be achieved throughadjusting and optimizing the numbers, B and D, of the basic amplifyingunits in the basic amplifying unit arrays 407 and 416, and the biasvoltages 408 and 417.

In the examples, the number A should be greater than or equal to zero,but less than A+B. The number C should be greater than or equal to zero,but less than C+D.

Furthermore, if there is a plurality of different linear modes, thepredetermined basic amplifying units can still be turned on throughconfiguring the bias voltages, and realize the optimum performance ofdifferent linear modes through adjusting and optimizing the biasvoltages. For example, when the multimode PA is operating in linearmode, it must cover different telecommunication standards (e.g. EDGE,WCDMA, TD-SCDMA, or TD-LTE), or meet the requirements of different power(gain) modes in a specific telecommunication format. It can be achievedthrough dividing the basic amplifying unit arrays 407 and 416 (or otherbasic amplifying unit arrays) into smaller basic amplifying unit arrays,adjusting the bias voltages of the smaller basic amplifying unit arraysindividually, and adjusting and optimizing the number of basicamplifying units that are on or off, or the bias voltages of the basicamplifying units that are turned on.

FIG. 5 shows a circuit diagram of a multimode PA with a three-stageamplifier circuit. The three-stage amplifier circuit comprises afirst-stage amplifier circuit 505, a second-stage amplifier circuit 510,and a third-stage amplifier circuit 519, connected with each other incascade. The first-stage amplifier circuit is a basic amplifying unitarray 505, comprising E (a positive integer) basic amplifying unitsconnected in parallel. A RF signal input terminal 501 connects to thebasic amplifying unit array 505. A supply voltage terminal 502 couplesRF signals to an RF signal input terminal 504 of an amplifier circuit510 at the second stage through an inductor 503. A bias voltage 506provides direct current bias to the basic amplifying unit array 505. Areference voltage 507 provides reference voltage to the basic amplifyingunit array 505. The amplifier circuit 510 at the second stage comprisesbasic amplifying unit arrays 511 and 513 connected in parallel. Thebasic amplifying unit array 511 comprises F (a positive integer) basicamplifying units connected in parallel, and the basic amplifying unitarray 513 comprises G (a positive integer) basic amplifying unitsconnected in parallel. A bias voltage 512 provides direct current biasto the basic amplifying unit array 511, and a bias voltage 514 providesdirect current bias to the basic amplifying unit array 513. A referencevoltage 515 provides reference voltage to the basic amplifying unitarrays 511 and 513 respectively. A supply voltage terminal 508 of theamplifier circuit 510 at the second stage couples RF signals to the RFsignal input terminal of an amplifying circuit 519 at the third stagethrough an inductor 509. The amplifying circuit 519 at the third stagecomprises basic amplifying unit arrays 520 and 522 connected inparallel. The basic amplifying unit array 520 comprises H (a positiveinteger) basic amplifying units connected in parallel, and the basicamplifying unit array 522 comprises I (a positive integer) basicamplifying units connected in parallel. A bias voltage 521 providesdirect current bias to the basic amplifying unit array 520, and a biasvoltage 523 provides direct current bias to the basic amplifying unitarray 522. A reference voltage 524 provides reference voltage to thebasic amplifying unit arrays 520 and 522 respectively. At a node 525,the amplifier circuit 519 at the third stage connects to the supplyvoltage terminal 517 through an inductor 518, couples RF signals to anoutput matching network 526, and completes outputting signals at a RFsignal output terminal 527.

When the multimode PA shown in FIG. 5 is operating in saturation mode,the basic amplifying units in the basic amplifying unit arrays 505, 511,513, 520 and 522 are turned on. Therefore, a specific performancerequirement can be achieved through adjusting and optimizing thenumbers, E, F, G, H, I, of the basic amplifying units in each basicamplifying unit arrays, and the corresponding bias voltages 506, 512,514, 521 and 523. In the saturation mode, all the basic amplifying unitsin the amplifier circuit 505 at the first stage, the amplifier circuit510 at the second stage, and the amplifier circuit 519 at the thirdstage operate regularly. The bias voltages 506, 512, 514, 521 and 523 ofthe basic amplifying unit arrays 505, 511+513, and 520+522 can bedetermined based on the technical requirements of the amplifyingtransistors.

When the multimode PA of FIG. 5 is operating in linear mode, the basicamplifying units in the basic amplifying unit arrays 511 and 520 can bestopped through controlling the bias voltages 512 and 521. The basicamplifying units in the basic amplifying unit arrays 505, 513 and 522can be turned on through controlling bias voltages 506, 514 and 523.Corresponding technical requirements can be achieved through adjustingand optimizing the numbers, G and I, of the basic amplifying units inthe basic amplifying unit arrays 513 and 522, and the bias voltages 506,514 and 523.

The number G is greater than or equal to zero, but less than F+G. Thenumber I is greater than or equal to zero, but less than H+I.

If the multimode PA operating in linear mode must cover differenttelecommunication standards (e.g. EDGE, WCDMA, TD-SCDMA, or TD-LTE), ormeet the requirements of different power (gain) modes in a specifictelecommunication standard, it can divide the basic amplifying unitarrays 513 and 522 (or other basic amplifying unit arrays) into smallerbasic amplifying unit arrays, adjust the bias voltages of the smallerbasic amplifying unit arrays individually, and adjust and optimize thenumber of basic amplifying units that are on or off, or the biasvoltages of the basic amplifying units that are turned on.

In most cases, the first-stage amplifier circuit is not changed becauseof the possible influence of the input impedance. But the performancecan still be optimized through adjusting the bias voltage 506accordingly. For example, if the bias voltages 512 and 521 are at a zerovoltage level, then the basic amplifying unit array 511 in the amplifiercircuit 510 at the second stage and the basic amplifying unit array 520in the amplifier circuit 519 at the third stage can be turned off. Inaddition, parameter G of the basic amplifying unit array 513, parameterI of the basic amplifying unit array 522, and the level of the biasvoltages 514 and 523 can be determined according to the specificperformance requirements imposed by the linear mode.

FIG. 6 shows a circuit diagram of a multimode PA with a four-stageamplifier circuit. The multimode PA has a first-stage amplifier circuit605, a second-stage amplifier circuit 610 and a third-stage amplifiercircuit 619, whose internal structure and operating principle isbasically the same as that of the multimode PA shown in FIG. 5, thus nofurther explanation is provided here. The amplifier circuit 628 at thefourth stage, connecting to the amplifier circuit 619 at the third stagein cascade, has the same internal structure and operating principle asthe circuit 619. When the multimode PA of FIG. 6 is operating insaturation mode, all the basic amplifying units in the basic amplifyingunit arrays 605, 611, 613, 620, 622, 629, and 631 are turned on.Corresponding performance requirements can be achieved through adjustingand optimizing the numbers, J, K, L, M, N, O, P (all are positiveintegers), of basic amplifying units and the level of bias voltages 606,612, 614, 621, 623, 630 and 632.

When the multimode PA of FIG. 6 is in linear mode, basic amplifyingunits in the basic amplifying unit arrays 611, 620 and 629 can bestopped through controlling the bias voltages 612, 621 and 630. Thebasic amplifying units in the basic amplifying unit arrays 605, 613, 622and 631 can be turned on through controlling the bias voltages 606, 614,623 and 632. Therefore, corresponding technical requirements can beachieved through adjusting and optimizing the numbers, L, N, P, of thebasic amplifying units in the basic amplifying unit arrays 613, 622 and631, and the bias voltages 606, 614, 623 and 632.

The number L is greater than or equal to zero, but less than F+L. Thenumber N is greater than or equal to zero, but less than M+N. The numberP is greater than or equal to zero, but less than O+P.

If the multimode PA operating in linear mode must cover differenttelecommunication standards (e.g. EDGE, WCDMA, TD-SCDMA, or TD-LTE), ormeet the requirements of different power (gain) modes in a specifictelecommunication standard, it can divide the basic amplifying unitarrays 613, 622 and 631 (or other basic amplifying unit arrays) intosmaller basic amplifying unit arrays, adjust the bias voltages of thesmaller basic amplifying unit arrays individually, and adjust andoptimize the number of basic amplifying units that are on or off, or thebias voltages of the basic amplifying units that are operatingregularly.

FIGS. 4, 5 and 6 show embodiments of the multimode PA with a two-stage,three-stage or four-stage circuit respectively. However, the multimodePA is not limited to the given number of stages. In fact, the amplifiercircuit at each stage comprises one or more basic amplifying unit arraysshown in FIG. 2, and connects to the amplifier circuit of other stagesin cascade, thus a multimode PA of any stage of amplifier circuit ispossible. Therefore, the multimode PA is able to adapt to differentrequirements imposed by different telecommunication standards or power(gain) modes.

The multimode PA can be used in mobile terminals as an importantcomponent of the RF circuit. “Mobile terminals” herein refers tocomputing devices that can be used in a moving environment and supportsa plurality of telecommunication standards, including EDGE, WCDMA,TD-SCDMA, and TD-LTE, such as mobile phones, laptops, tablets, or carcomputers. In addition, the multimode PA can also be applied to otherplaces where multimode technology is involved, such as base stationsaccommodating different telecommunication standards.

The multimode PA, the method of switching among multiple modes thereofand the mobile terminals using the multimode PA provided by the presentinvention have been explained in detail. Under the premise of staying inline with the substantive spirit of the present invention, any obviouschange done by any regular technician in this field constitutes aninfringement to the patent of the present invention. The violators shallbe held accountable to the corresponding legal responsibility.

What is claimed is:
 1. A multimode power amplifier (PA), comprising twoor more stages of amplifier circuits connected in cascade, wherein: eachamplifier circuit comprises one or more basic amplifying unit arraycomprising a plurality of basic amplifying units connected in parallel;each basic amplifying unit comprises a capacitor, a amplifyingtransistor and a resistor, wherein the capacitor connects, at one end,the radio frequency (RF) signal input terminal, and at another end, abase of the amplifying transistor; the resistor connects, at one end, abias voltage terminal, and at another end, the base of the amplifyingtransistor; a collector of the amplifying transistor connects a supplyvoltage terminal; an emitter of the amplifying transistor of each basicamplifying unit connects a reference voltage; a bias voltage of eachbasic amplifying unit array is controlled independently; an inductor isinstalled between the supply voltage terminal of the amplifier circuitof a previous stage and a RF signal input terminal of the amplifiercircuit of a next stage; the supply voltage terminal of the amplifiercircuit of the previous stage couples the RF signals to the RF signalinput terminal of the amplifier circuit of the next stage.
 2. Amultimode PA comprising two or more stages of amplifier circuitsconnected in cascade, wherein an amplifier circuit at each stagecomprises one or more basic amplifying unit array comprising a pluralityof basic amplifying units connected in parallel; a basic amplifying unitcomprises a capacitor, an amplifying transistor and a resistor, whereinthe capacitor connects between a RF signal input terminal and a base ofthe amplifying transistor; the resistor connects between a bias voltageterminal and the base of the amplifying transistor; a collector of theamplifying transistor connects a supply voltage terminal; a bias voltageof each basic amplifying unit array is controlled independently.
 3. Themultimode PA of claim 2 wherein the supply voltage terminal of anamplifier circuit of the previous stage couples RF signals to the RFsignal input terminal of an amplifier circuit at the next stage.
 4. Themultimode PA of claim 3 wherein an inductor is installed between thesupply voltage terminal of the amplifier circuit of the previous stageand the RF signal input terminal of the amplifier circuit of the nextstage.
 5. The multimode PA of claim 2 wherein an emitter of theamplifying transistor of the basic amplifying unit connects to areference voltage.